How to Make Glow Effect to Fade?
Here's one way. This assumes that the long axis of your glow stick is the Z axis.

The Texture Coordinate node will give you a value for each dimension that varies between 0 and 1, in the form of a color map.

The separateXYZ node will give you just the Z value.

The ColorRamp converts that value into a single color.

My color ramp goes from black to white, but you can change the color


Select the color ramp
click in the vicinity of one of the two pointers
click on the color patch just about the Fac input
Select a color from the color picker


There are many ways to adjust the color ramp.  You can move the pointers around.  THe most useful to you might be that moving the right pointer farther left will reduce the area where the fade happens.